Mayor Rahm Emanuel’s idea of expanding Soldier Field was met with questions Wednesday about how the city would pay for added seats and whether it’s a prudent move given the city’s shaky finances.

The administration’s stadium concept surfaced Tuesday as a major ratings agency downgraded the city’s credit, citing a huge debt for police and firefighter pensions that’s about to come due and the borrowing City Hall does each year to paper over budget shortfalls.

Adding to Soldier Field’s lowest-in-the-NFL seating capacity could be a way to help Emanuel reach his goal of hosting a Super Bowl in Chicago. The mayor has lobbied NFL Commissioner Roger Goodell to give the city that plum.

On Wednesday, however, Emanuel sought to frame a potential Soldier Field expansion as a way to boost other events the Chicago Park District-owned stadium has hosted.

“It’s an idea to discuss and analyze,” Emanuel said. “Soldier Field, beyond the Chicago Bears, has been a place for soccer games, hockey games, concerts and other sporting events, and we are capped for what type of other events we can attract, because of the size.”

When asked what events, other than the Super Bowl, were bypassing the city and Soldier Field because of its 61,500-seat capacity, Emanuel changed course.

“What started this was how quickly these other events have sold out, and we could have done more,” Emanuel said of concerts and the Chicago Blackhawks outdoor game at Soldier Field last weekend. “Will it allow us (to host a Super Bowl)? Yes, but it’s not for that solely.”

Soldier Field was rebuilt after a 2001 state deal that saw the Illinois Sports Facilities Authority borrow what was billed as $399 million for the $690 million project. The loan is being repaid through a hotel tax, though the city is on the hook if there is a shortfall, which agency officials said happened three years ago.

Ald. Robert Fioretti, 2nd, whose ward currently includes Soldier Field, said no taxpayer money should be used to expand the lakefront stadium. He pointed to Moody’s decision Tuesday to downgrade the city’s credit rating once again as evidence the city is in “a serious bind.”

Ald. Will Burns, 4th, whose ward would include Soldier Field when new city redistricting goes into effect in 2015, said he could see the economic benefits of a Super Bowl but wants to know what kind of borrowing authority the park district currently has available and whether amusement tax dollars would be used to help fund the project.

The mayor declined to say how a Soldier Field expansion could be funded, saying those questions were premature because the city and Chicago Park District first would have to determine if the plan was feasible.

City Hall kept a tight lid on the issue Wednesday. Emanuel said Park District Superintendent Mike Kelly came to him with the idea to study the issue. But Kelly, through a spokeswoman, referred all questions about Soldier Field to the mayor’s press office.

The Bears weren’t saying much either. “If it makes sense to add seats,” team spokesman Scott Hagel said, “we would be open to the idea.”

There certainly would seem to be a market for more seats at Bears games, given the team’s long season ticket waiting list and continued sellout streak despite increasing season ticket prices nearly every year since 2003.

Emanuel said his original notion of adding 5,000 seats is just a starting point, and that after more research, it may be deemed 7,000 seats is better or the decision may to be add zero seats. He also added that architectural studies hadn’t been conducted yet.

Allen Sanderson, a sports economist at the University of Chicago, said adding 5,000 seats would not pass a cost-benefit analysis.

“Putting 5,000 more seats in this stadium would be like putting lipstick on a pig — lipstick on an ugly pig,’” said Sanderson, who argued the city botched the 2003 stadium renovation design and budget.

“The city can gin up things like the Blackhawks-Penguins game, but you just can’t get a high enough utilization rate to get a return on investment.”

Since the beginning of 2011, the Park District reports there have been just 20 major events other than Bears games held at Soldier Field and only nine were sellouts. Of those sellouts, four were concerts that had thousands of seats blocked off because of stages or obstructed views.

If the city was serious about competing for a Super Bowl, Sanderson said, Emanuel would be better off tearing down Soldier Field and building a larger stadium with a retractable roof on a less valuable parcel of land elsewhere in the city. Then Chicago could also bid for revenue generators like the NCAA Final Four. That battle, however, was fought and lost more than a decade ago.

For his part, the mayor sought to stress the preliminary nature of the Soldier Field expansion talk.

“Before you get to how you pay for something, I’m asking a more fundamental question, ‘Does it make sense?’” the mayor said. “And if it does make sense, I didn’t say how we’re going to finance it. That’s a whole other question.”

Chicago’s financial standing took a hit Tuesday when a major bond rating agency once again downgraded the city’s credit worthiness because of a huge government worker pension shortfall and the overall amount of money it owes.